1. Field of the Invention
The field of the invention relates to drilling rigs for the drilling of oil, gas and other wells, and in particular to drilling rigs having modular components which are capable of being moved from well to well in formation.
2. Description of the Related Art
In drilling oil and gas wells, it is well known that almost innumerable components are essential to actually drilling the well. For example, a basic drilling rig structure having a mast housing rotational equipment such as a top drive is necessary to direct the drill pipe and casing strings into the borehole as drilling takes place. In order to circulate the drill cuttings out of the borehole during drilling, it is necessary to circulate drilling “mud” or fluid down the drill pipe and upwardly through the annulus between the drill pipe and the casing. Providing the mud circulation system requires powerful mud pumps, fluid storage equipment, and particle separation equipment to remove the drill cuttings and prepare the drilling mud for recirculation.
The top drive and most other well equipment are electrically powered, thus requiring significant power generation equipment. For example, referring to FIG. 2 of U.S. Pat. No. 4,899,832, the drilling unit includes massive pipe storage units, a mud mixing and supply unit, first and second electrical power supply units, a drilling mud return unit, a fuel unit, a water supply unit, a cement unit and a command center, which must be set up at each drill site, and then transported on truck tractors to the next well site and then set up again in the necessary arrangement for drilling activity. Typically in the U.S., such equipment must be broken down into loads which meet allowable weight and size restrictions for travel along state and federal roads.
In some foreign countries where the drilling sites are located on remote land such as in the Artic or in the deserts of the Mid-East, because the drilling rigs and associated equipment do not have to travel along highways, it is known to use portable drilling rigs in which the drilling equipment is housed in travel modules. For example, Dreco, now a part of National Oil Well Varco, utilized modular type construction of the drilling rig and drilling equipment such that the modules could be disassembled and loaded onto trucks, islands, barges, and/or caissons for travel between well sites. The Dreco portable rigs utilized giant wheel assemblies, which included all wheel drive, to move the rigs over the country side, but insofar as known, the modular components were moved without attempt to maintain the modules in drilling formation or arrangement during travel. For example, Dreco's Desert Rigs were moved from well to well in a single line formation using a combination of truck tractor and wheel units mounted directly with the drilling modules. Once a new drill site was reached, while major equipment did not need to be removed during transportation, it was then necessary to demobilize the modules and arrange them into the formation necessary to begin drilling operations.